Field
This invention relates to the production of minerals, more specifically, to the production of hydrocarbons, by hydraulic fracturing of the rock, and can be used for the optimization of formation fracturing crack processing conditions.
Background
Hydraulic fracturing is currently the main method of increasing well delivery by producing new or expanding the existing highly permeable cracks initiating from the well bore to the reservoir bulk.
The standard hydraulic fracturing comprises, as the first step, pumping the working fluid at high pressure and pumping rate into the rock until a crack is initiated in the rock. The second stage comprises pumping the propping agent into the hydraulic fracturing crack so produced. After the fluid pressure is reduced at the end of the overall procedure, the propping agent particles delivered to the crack form a uniform pack and prevent the crack for complete closure.
The permeability of a propping agent packed crack is higher than that of the country rock. Although this method has been known and widely used for many years now, there situations where further increasing the permeability of the propping agent pack to above that provided by the standard technology would provide for a serious economic advantage.
Various well delivery increasing methods are known today.
Known (SU Inventor's Certificate 467173) is a bottomhole formation zone heat treatment method. Under said known method, the bottomhole zone heat treatment procedure comprises pumping a highly heat conductive heat carrier into the formation, such heat carrier being a granulated material, for example, metallic powder acting as the propping agent. The grain size and distribution of said metallic powders are selected based on their pumping efficiency and penetrability into the formation cracks. The prepared suspensions do not penetrate into the pore channels but fill the existing and pumping initiated cracks in the bottomhole formation zone. After a system of granulated metallic powder filled cracks has been produced in the formation, an electric heater is lowered into the well to heat the bottomhole zone.
Said method is complex in implementation because in fact it comprises two stages, i.e. first hydraulic fracturing and then metallic powder pumping into the cracks. Its low efficiency is predetermined by the fact that in order for metallic powder into the cracks, low forces are used that are developed by the volume expansion of the bottomhole zone fluid during heating; therefore heating penetrates to small distances inward the formation.
Known also (U.S. Pat. No. 6,114,410) is a method of increasing the permeability of the formation hydraulic fracturing crack. According to said known method, adhesion of corrosion capable particles are introduced into the propping agent. Said adhesive particles may have a vulcanized resin coating. Said adhesive particles come in contact with similar adhesive particles to form a stable and strong matrix that produces propping agent structures in the crack. This increases, though slightly, the crack permeability and generally improves the efficiency of hydraulic treatment.
However, the efficiency of said method is low.